Various types of antibacterial members have been developed and turned into products to reduce microbes in the environment because of increased consumers' consciousness of hygiene. In general, antibacterial members used for interior members in houses or vehicles contain antibacterial materials such as silver and zinc. However, silver and zinc have a problem of costs or biological toxicity.
In view of such a problem, attempts to use cuprous oxide for antibacterial materials or virus inactivation agents are being developed, since an abundance of low-cost cuprous oxide with less biological toxicity is available (for example, refer to Patent Literature 1). However, the cuprous oxide is commonly used for concealing paint such as enamel for ship bottom painting because the cuprous oxide cannot be dispersed easily. In order to increase dispersibility, a method for producing a Cu2O nanoparticle dispersion liquid by way of microemulsion has been disclosed (for example, refer to Patent Literature 2).